Lateral deformation and associated settlement resulting from embankment loading of soft clay and silt deposits

Settlement of structures on soft clay deposits results from flow and consolidation of soil. In the latter case, water squeezes out from under the structure, whereas in the former case soil squeezes out. Settlement resulting from flow of soil depends on the factor of safety against undrained instability. In construction situations where the factor of safety is small, an accurate prediction of settlement resulting from flow of soil is required. Field measurements of horizontal deformation of soft clays during and after construction of embankments and storage facilities have been collected from throughout the world, covering 180 case histories, to relate lateral deformation to the factor of safety and to develop a practical procedure for computing settlements resulting from flow of soil.; The available methods for predicting the undrained settlement and lateral deformation, including solutions based on elasticity, empirical procedures, and numerical techniques, were reviewed. The behavior of clay foundations subjected to embankment loading and empirical methods using lateral deformation as a measure of undrained stability, were reviewed and discussed.; The 180 case histories of embankments on soft clay and silt deposits with lateral deformation measurements cover a wide range of subsurface conditions, including plasticity index Ip from 5 to 340, undrained shear strength s _u from 5 to 80 kPa, E_u/s_u from 200 to 1000, σ ′_p/σ′ _vo from 1 to 5, embankment width B from 8.5 m to 630 m embankment height h from 1 to 35m, embankment slope width L from 1.35 to 195 m, and depth of foundation L_o, from 7 to 63 m.; An empirical correlation, based on 58 cases was developed between maximum lateral deformation D_m or area of lateral deformation profile A _D and factor of safety against undrained failure. Parameters such as E_u, L, B/2 were also included in the correlation.; A procedure, based on 16 cases with three or more inclinometers at several distances from the centerline, was developed for determining distribution of maximum lateral deformation and flow settlement across the embankment as a function of Lo/B and L/0.5B. The procedure could be used either with one inclinometer measurement e.g. near the toe of the embankment, or together with the empirical correlation between D_m and factor of safety.; A procedure was developed for determining settlement trough resulting from lateral deformation of soil out from under the embankment. The procedure could be used together with inclinometer measurements at one location, e.g. near the toe of the embankment or with D_m or A_D determined from the empirical correlation between lateral deformation and factor of safety.; Using the empirical database and the developed procedures, it was possible to make successful prediction of lateral deformation and associated settlement for embankments on soft clay and silt deposits.